Exhalation valves are an essential part of respiration devices. They carry air or oxygen to the patient and carbon dioxide from the patient to atmosphere. The function of the exhalation valve in respiration devices is to allow a patients exhaled breath to vent to atmosphere, while preventing gas being supplied to the patient from venting to atmosphere before it reaches the patient. Exhalation valves currently In the art have a number of drawbacks.
Prior art valves generally are unable to function accurately as pressure control devices since they usually operate in two extreme positions only; namely open or closed. These valves are not well suited for any incremental operation.
Valves in the current art usually perform with a noticeable lag time between initialization of the respiration process and response time of the valves.
Exhalation valves known in the prior art exhibit a linear relationship between the control signal and the servo mechanism. They are noisy in operation and tend to malfunction. This is generally due to blockage of exhalation discharge to atmosphere, improper assembly after disassembly for cleaning and or sterilization, or a combination of these factors.
An example of a valve in the current art may be found in U.S. Pat. No. 4,717,117 to Cook entitled "Vacuum Valve Using Improved Diaphragm." The subject valve employs a flexible diaphragm for opening and closing an exhalation port, and exhibits most of the drawbacks mentioned above.